Air cooling for thermionic tubes



s- 18, 1942. J. L. FINCH 2,293,497

AIR.COOI.;ING FOR THERMIONIC TUBES Original Filed June 16. 1936 INVENTQRJAMES LESLIE FINCH I BY mu ATTORNEY Patented Aug. 18, 1942 2,293,497 AIRCOOLING FOR THERMIONIC TUBES James Leslie Finch, East Rockaway, N. Y.,assignor to Radio Corporation of America, a corporation of DelawareOriginal application 214,003. Divided June 16, 1938, Serial No. and thisapplication September 13, 1940, Serial No. 356,606

Claims.

This invention relates to a novel and improved method for the cooling ofmetal anodes of thermionic tubes in an efiective and eflicient manner.

This is a division of my copending application Serial No. 214,003, filedJune 16, 1938, and patented Jan. 21, 1941, Patent #2,229,446, which is adivision of the parent application, Serial No. 126,124, filed Feb. 17,1937, now United States Patent #2,176,657.

The claims in this application are directed to the circular casingarrangement.

An object of this invention is to simplify and improve the cooling ofthermionic tubes generally by means of circulating air.

Another object of this invention is to provide an improved air coolingsystem for the cooling of thermionic tubes having electrical controlcontacts associated therewith.

Still another object of this invention is to improve the cooling of thevacuum tube by reducing the number of component parts required in acooling system and thereby reducing the cost thereof.

In the prior art, a vacuum tube was generally cooled by a systememploying a liquid medium, such a system requiring a second cooler forthe liquid and numerous insulating connections for carrying the liquidfrom the point of the source to and around the anode of the tube. Whendirect air cooling has been used, it has been found inefiective andresults in a reduction of the allowable output of the tubes.

Briefly, this invention comprises a system having a source of airsupply, such as for example, a blower or fan, a chamber, and asupporting means for the tube, the supporting means being arranged witha plurality of curved radiating fins.

The outside contour of the supporting members is in two forms, one beingrectangular and the other circular. The circular form provides a moreeconomical unit for the same spacing, although it is not quite asefiicient as the rectangular surface which gives a slightly bettercooling, due to the greater surface area of the cooling fins.

Electrical control contacts are located adjacent the cooling system andarranged to break the power supply circuit when undesired temperaturesare reached.

This invention will best be understood by referring to the accompanyingdrawing, in which:

Fig. 1 is av sectional view of an improved air cooling system;

Fig. 2 is a. sectional view of another embodiment of this invention;

Fig. 3 is a sectional view of a further embodiment of this invention;and

Fig. 4 is a plan view of Fig. 1, showing a circular support and airchamber.

Referring now in detail to the drawing, l is a metal anode of athermionic tube, 2 indicates its glass envelope, 3 is the grid lead and4 and 5 the cathode and filament leads. Anode l is sealed into asuitable cavity formed in a metallic block 6 by means of some fusiblemetal, such as solder. Anode l is held in place by clamps l and 8 whichserve to additionally hold member I in place, should the sealingmaterial or solder melt at the rim portion thereof. The equivalentcontour of block member 6 is in the form of a truncated cone and isfitted tightly within a conical aperture in metallic hub 9. Member 6 isfirmly secured to hub member 9 by means of a stud l0, clamping spring IIand nut l2. These clamping members can be removed with the tube when itis necessary to change the tube. Hub member 9 is provided with an extralarge outer diameter. This provides a massive metal hub having across-section greater than block 6, which allows heat generated in anodel to travel through it to the ends of a large number of cooling fins ISwith a minimum temperature drop. The fins l3 are soldered into slots inthe periphery of hub 9 and leave the slots in approximately a radialdirection, and are also curved so as to keep the space between adjacentfins approximately parallel or equal throughout their length, whicharrangement gives an increased cooling area, and also maintains the airfriction between the fins approximately the same throughout the wholesectional area of the cooling system. The outer ends of the fins aresecured to an enclosing and supporting member I 4; as mentioned above,this may be rectangular or circular in form. A fan l5, driven by a motorI6, forces air upward and around the fins l3, thus carrying away theheat generated in anode I. Surrounding the fan is a duct or container H,which may be of metal or transparent insulating material, such as glass.The lower end of I! is preferably of circular section and fits closelyaround the blades of the fan l5, or, in the case of a blower, around themanifold. The upper end of duct I1 is of a section corresponding to thatof the outside contour of supportin member M. The spacing betweenmembers l4 and I1 is enclosed by a duct l8, made preferably ofinsulating material, having the requisite insulating characteristics forwithstanding the voltage normally placed upon the member l4 and alsobeing of suitable size for confining the stream of air from the fan sothat the most of it passes through the cooling fin area. Member I8 isremovable, at least in part, to allow replacement of tubes, and it ispreferable that member i8 be made of glass or other transparentinsulating material, in order that the inside be visible. The filamentleads 4 and 5 are preferably brought out through bushings in the wallsof member [1, while the grid lead 3 is brought out through an aperturein member l8.

Associated with the cooling unit, is an air flow trip l9 which closes acircuit between member [9 and contact 20, when the force of air reachesabove that of a predetermined value, and allows the circuit to open whenthe flow is below a predetermined value. A thermostat 2! is alsoassociated with member I4 and is located in such a position that with orwithout the fan running normally, any excess in temperature will causethe circuit between members 2| and 22 to open, while normal temperatureswill allow this circuit to remain closed. These two circuit devices areso connected in the electrical circuit that the power will be removedfrom the device in the case of failure of the cooling air, or in thecase of an excess temperature due to any cause.

The modification shown in Fig. 2 is generally similar to that of Fig. 1,except that the air duct l8 can be dispensed with for the reason thatthe area of the fin section is tapered outwardly toward the top, theupper area being greater where the air leaves than where it enters. Ablast of air from the fan directed against the intake of the fins hasstored in it kinetic energy, and as this air passes through theexpanding fin area, its velocity decreases and therefore emerges at areduced velocity. This decrease in velocity represents a transfer ofenergy and this transfer is arranged so as to be substantiallysufficient to supply the energy required to overcome the friction of airpassing between the fins l3; thus, no difference in pressure is requiredto force the air through the fins and therefore, essentially all of theair directed to the fins will pass through them, whereas without thistaper, the pressure would have to be greater at the intake than at theexhaust. Since the exhaust pressure will be atmospheric, the intake willhave to be above atmospheric. This would result in only a part of theair from the fan I 5 passing through the fins, if the ducts l1 and M3were omitted.

A still further modification is shown in Fig. 3. In this modification,member I8 is also dispensed with, and the area through the fins properdoes not expand, and although this modification is not as efiicient asthat of Fig. 2, it is slightly more economical to construct than thatshown in Fig. 2. To compensate for the omission of taper 14, a duct 23is placed at the intake side. The

area of the intake of duct 23 is less than that of the fins. The streamof air from the fan is directed at this opening. After entering, itslows down, due to the increased area and the kinetic energy thusexpended is converted into potential energy in the form of pressure.Thus, while the pressure at the entrance of 23 is atmospheric, at theentrance of the fins it is somewhat above atmospheric. This pressureovercomes the friction through the fins.

An improving cooling or radiating member is shown by Fig. 4. The vanesl3 are provided to give substantially equal spacing by the use of acurve member radially spaced. It will be noted that from a desireddistance from the anodes, the

vanes run substantially parallel, at which point the most effectivecooling is obtained. By the use of the curved vane, a greater cooling ofthe tube can be obtained for the same amount of space and air pressurethan if the cooling fins or vanes were only straight and arrangedradially.

While only a few modifications of this invention have been disclosed, itis to be distinctly understood that it is capable of taking other formswithin the spirit and scope thereof.

What is claimed is:

1. A cooling system comprising an electron discharge device having atleast an anode and cathode, a metallic sleeve surrounding said anode, ametallic hub member surrounding said sleeve, a circular metallic bandconcentrically surrounding said anode and said hub member, a pluralityof slots in said hub member, a plurality of radiating fins extendingoutward and located to be substantially equally and parallelly spacedfrom each other, said metallic band supported to and connecting theoutside ends of said fins, and means for supplying cooling air to saidtube by a device located adjacent said metallic member.

2. In an air cooled thermionic tube, means for transferring heat fromsaid tube to the surrounding air, comprising a plurality of circularcasing members, a plurality of fins arranged to maintain substantiallyuniform spacing throughout their length, the outer ends of said finsterminating and secured to at least one of said casing members, all ofsaid casing members arranged one above the other for confining the airsurrounding said tube.

3. In an air cooled thermionic tube, means for transferring heat fromsaid tube to the surrounding air, comprising a plurality of circularcasing members, a plurality of fins arranged to maintain substantiallyuniform spacing throughout their entire length, at least one of saidcasing members being in the form of a circular metallic bandconcentrically arranged with respect to said tube, the outer ends ofsaid fins terminating and secured to said metallic band, all of saidcasing members arranged one above the other for confining the airsurrounding said tube.

4. In combination, a thermionic tube having at least an anode andcathode, a metallic sleeve in intimate thermal conact with said anode, ametallic hub member surounding said sleeve, a circular metallic bandsurrounding said hub memher, a plurality of metallic fins radiallyextending outwardly from said metallic hub member and joined to saidband, an insulating duct disposed below said metallic band, and animpeller for forcing a stream of air to flow between said fins and saidduct member so as to confine the air discharge to the area between thefins.

5. An electron discharge device cooling system for use in a radiotransmitter, said electron discharge device having at least anode andcathode, a plurality of circular casing members, a metallic sleevesurrounding said anode, a metallic hub member'surrounding said sleeve, aplurality of.

metallic sleeve surrounding said anode, a metallic hub membersurrounding said sleeve, a plurality of radiating fins extendingoutwardly from said metallic hub member and secured to one of saidcasing members, means for supplying cooling air to said dischargedevice, said means comprising an impeller located adjacent said metallichub member, and a plurality of electrical contacts located adjacent saidmetallic hub member, said contacts being secured to one of said casingsand arranged in an electrical circuit, a device responsive totemperature connected in said electrical circuit, saidtemperature-responsive device being connected and so located withrespect to said anode that it responds to the temperature of the finswhether the impeller is in operation or not, to control the heat beingliberated in the tube anode.

7. In an air cooled thermionic tube, comprising means for transferringheat from said tube to the surrounding air, a metallic hub membersurrounding said tube, a plurality of curved fins arranged to radiallyextend out from said hub member to maintain the spacing of said fins,said fins being curved to be of a greater length than the shortestradial distance between the hub and said metallic band and located to bespaced apart from an adjacent fin, a shell of circular crosssection forsupporting and for confining the cooled air.

8. A cooling system comprising an electron discharge device having atleast an anode and cathode, a metallic sleeve surrounding said anode, ametallic hub member surrounding said sleeve, a circular metallic bandsurrounding said hub member, a plurality of radiating fins extendingoutwardly from said metallic hub member to join said metallic band, eachof said fins being curved to be of a greater length than the shortestradial distance between the hub and said metallic band, and means forsupplying cooling air to said discharge device by a member locatedadjacent said metallic hub member, the area of said fins beingsubstantially greater where the cooling air leaves than at the pointwhere it enters.

9. A cooling system comprising an electron dis charge device having atleast an anode and cathode, a metallic sleeve surrounding said anode, ametallic hub member surrounding said sleeve, a circular metallic bandsurrounding said hub member, a plurality of radiating fins extendingoutwardly from said metallic hub member to join said metallic band, eachof said fins being curved to be of a greater length than the shortestradial distance between the hub and said metallic band and located to bespaced apart from an adjacent fin, and means comprising an impeller forsupplying cooling air to said discharge device by a member locatedadjacent said metallic hub memher, the area of said fins beingsubstantially greater where the cooling air leaves than at the pointwhere it enters, said fins being arrangedto receive the air from saidimpeller.

10. A cooling system comprising an electron discharge device having atleast an anode and cathode, a metallic sleeve surrounding said anode, acircular metallic hub member surrounding said sleeve, a circularmetallic band surrounding said hub member, a plurality of radiating finsextending outwardly from said metallic hub member to join said metallicband, each of said fins being curved to be of a greater length than theshortest radial distance between the hub and said metallic band andlocated to be spaced apart from an adjacent fin, and means comprising animpeller for supplying cooling air to said discharge device by a memberlocated adjacent said metallic hub member, a circular duct member havingsloping side walls located below said metallic band so that saidradiating fins receive the air from said impeller.

JAMES LESLIE FINCH.

